Shaped charge explosive unit and liner therefor



T. c. POULTER 3,136,249

SHAPED CHARGE EXPLOSIVE UNIT AND LINER THEREFOR June 9, 1964 Filed June 12, 1961 Fig.2

INVENTOR Thomas C. PouHer ATTORNEY United States Patent Ofi ice 3,136,249 Patented June 9, 1964 3,136,249 SHAPED CHARGE EXPLOSIVE UNIT AND LINER THEREFOR Thomas C. Poulter, Palo Alto, Calif assignor to Jet Research Center, Inc., Arlington, Tex., a corporation of Texas Filed June 12, 1961, Ser. No. 116,612 3 Claims. (Cl. 102-24) This invention relates to shaped charge explosive devices and to metal liners for the cavities in shaped charge explosives.

Shaped charge explosive perforating units have been used for a number of years to perforate oil and gas Wells. One of the features of most of the shaped charge explosive units previously used for this service is the formation of a slug or carrot from a portion of the metal liner for the charge cavity. This carrot is formed near the rear of the jet particle stream generated when a shaped charge explosive unit having a metal cavity liner is detonated. The carrot or slug has a lower velocity than the forward portion of the jet particle stream and frequently has a smaller diameter than the perforation produced in the well casing so that it often follows the jet particle stream into the earth formation and lodges in the perforation. This is undesirable as it blocks off a portion of the perforation and reduces the flow of formation fluids into the well bore. Even more objectionable is the situation where the diameter of the slug is great enough to cause it to lodge in the hole in the well casing, completely blocking any flow from the earth formation into the casing.

Therefore, it is an object of this invention to provide a shaped charge explosive unit for perforating a well which is free from formation of a slug capable of plugging the perforation produced upon detonation of the unit.

It is another object of this invention to provide a metal liner for the face of the cavity of a shaped charge explosive unit that does not form a slug capable of plugging the perforation produced upon detonation of the unit.

The lined, shaped explosive charge of the present invention includes a body of explosive material providing a cavity in a face thereof and a metal liner covering the face of the cavity. The metal liner comprises a composition consisting essentially of from 75 percent to 99.5 percent copper and from 25 percent to 0.5 percent lead. This composition has a metallographic structure consisting of copper dendrites with the spaces between the dendrites filled with lead. The liner is adapted to break up substantially completely into small particles when the explosive material is fired.

The invention will be more fully described in the following detailed description of an embodiment thereof illustrated in the accompanying drawings.

In the drawings:

FIG. 1 is an axial, sectional view of a shaped charge explosive device in accordance with the present invention; and

FIG. 2 is a detailed, axial, sectional view of the liner of the shaped charge explosive device of FIG. 1.

Referring now to FIG. 1, a shaped charge unit, designated generally, is shown. The shaped charge unit has a case 11 made of any suitable material such as metal or plastic. The case has an open forward end 12 and is closed at the rear thereof. Inside the case is contained a suitable quantity of compressed detonating explosive material 13. A charge of booster explosive 14 is compressed in a booster cup 15 seated in a recess 16 in the rear of the charge case 11. An opening 17 is provided in the rear of the charge case through which may be threaded a length of detonating fuse (not shown) to fire the perforating device. A curved, disk-shaped barrier 18, of a suitable dense metal such as steel, is embedded in the explosive material about midway between the front surface 19 and the rear surface 20 of the explosive and is symmetrical with the longitudinal axis of the shaped charge device. A metal liner 21 covers the front concave surface 19 of the explosive material and contacts at its periphery 22 the inner wall 23 of the charge case 11 near the front of the case.

Referring now to FIG. 2, the metal linear 21 is shown in section and is substantially uniform in thickness over its entire area.

The metal liner 21 is made from a composition or alloy of copper and lead. It is known that lead is almost entirely insoluble in solid copper and only partly soluble in liquid copper. Molten mixtures of copper containing from about 0.5 percent to about 25 percent lead upon cooling will produce alloys in which the structure consists of copper dendrites with the spaces between the dendrites filled with lead. Such metals tend to be hot short and cold short so that they are workable only with care. These metals are not true alloys in the strict sense of the word. This can be readily determined by subjecting the copperlead metal to microscopic examination. In the molten state, the lead goes into solution in the copper and as the metal solidifies the lead separates out and distributes itself along the boundaries of the copper grains. The fact that copper-lead metal does not form a true alloy is responsible for the liner breaking up into many fine pieces instead of forming a slug or carrot. The low tensile strength lead along the grain boundaries weakens the cohesive tensile and shear strength between the copper grains or dendrites, thus causing the liner to break up into grain size particles and, at the same time, reducing the force necessary to extrude the metal from the form of the liner into a jet particle tream. Therefore, it is to be understood that all references herein to copper-lead alloy or alloy are to be construed in the light of the foregoing explanation.

Liners, in accordance with the invention, for shaped charge explosive devices may be made from alloys of copper containing lead from about 0.5 percent up to about 25 percent. The preferred copper-lead liners are produced from copper alloys containing from 0.5 percent up to 6 percent maximum lead. A typical composition has a lead content of 3.2 percent with the balance being copper.

The liners of the invention are fabricated by casting and machining the alloy. Alternatively, and preferably, the alloy may be rolled into sheets and formed to final shape by die-pressing blanks cut from the sheets.

A specific example of the invention is made by constructing a shaped charge device in strict accordance with the design shown in FIG. 1 of the drawings. The case 11 is die cast from a high zinc-base alloy and has an inside diameter of 1.698 inches at the front of the case with an overall length of 2.187 inches. The recess 16 for the booster cup 15 is 0.415 inch in diameter and 0.290 inch deep. The booster cup 15 containing 0.45 gram of compressed cyclonite is inserted in the recess 16. Four grams of cyclonite coated with about 3 to 5 percent microcrystalline wax is loaded into the case on top of the booster. A steel barrier 18 one inch in diameter is positioned centrally in the case on top of the four gram charge of waxed cyclonite. A further charge of 15 grams of waxed cyclonite is added to the case on top of the barrier. A linear 21 of 0.030 inch thickness is fabricated from a copper-lead alloy containing 3.2 percent lead. This liner is placed on top of the cylonite and pressed with a conforming punch powered by a total ram force of 312,000 pounds. The case 11 is supported by a close fitting, steel die during the compression step.

A shaped-charge device, constructed in accordance with dimensions. The target was cut open for examination and V no carrot or slug was found'therein.

Other shaped charge. units like" that described in. the foregoing specific example whenshotv into a soap foam tank leave in the tank all of the particles from the jets formed from the copper-lead alloy liners. The liner residue recovered from the tank shows that the liner is practically entirely disintegrated into small particles of about the size of common table salt. A few'fragments ofsomewhat larger size are also recovered. I i I The depths of the perforations obtained in a number of target shots using leaded-copper liners were comparable to those obtained in shots using a substantially pure copper liner in the same size shaped charge units.

From the foregoing, it is evident 'thata new and im proved shaped charge explosive unit .andliner therefor has been developed. While the liner shown and described is generally paraboloidal in shape, the use of leaded copper ,metal for liners of any shape is contemplated. Further, the present invention is not to be limited to the specific form of shaped charge unit herein described and depicted. 1

It is notnecessary that the shaped charge explosive unit utilize a barrier within the explosive material as shown in FIG. 1 of the drawings. The barrier is optionaland may be omitted if desired. Barrier charges are well known in the art and such units, per se, form no part'of the present invention. An improved barrier type shaped charge device similar to that shown in FIG. 1 is disclosed and claimed in the copending US. patent application of Thomas C.

Poulter, Serial No. 786,888, filed January 14, 1959, now

US. Patent No. 3,100,445, issued August 13, 1 963, for Shaped Charge and Method for Firing the Same, which is a continuation-in-partof the application of Thomas C.

' Poulter, Serial No. 439,564, filed June 28, 1954, now

abandoned, for Shaped Charge. The copending application Serial No. 786,888, now US. Patent No. 3,100,445,

is vassignedjointly to two corporations owning allthe capital stock of the assignee of the present application.

I claim: a 1. A lined, shaped explosive charge comprising: (a) a body of explosive material providing a cavity in a face thereof; and

(b) a metal liner covering the face of said cavity, said metal liner comprisinga composition consisting es dendritesfilled with lead, said linear being adapted to break, up substantially completely into small particles when said explosive material isfired. i 2. A lined, shaped explosive charge comprising: (a) a body of'explosive material providing a cavity in a face thereof; and 1 (b) a metal, liner covering the face of said cavity, said I 1 metal liner comprising a'composition consistingesse ntially of from 94percent to 99.5 percent copper and from 6 percent to 0.5 percent lead, said composition I having a metallographic structure consisting of COP, per dendritesiwith the spaces between said dendrites filled with lead, said" liner being adapted to break up.

7 substantially completely intosmall particles when said explosive material is fired. 3. A lined, shaped explosive charge comprising:

' V (a) a body of explosive material providing a cavity in a face thereof; and

(b) a metal liner covering the face of said cavity, said metal liner comprising acomposition consisting essentially of 96.8 percent copper and 3.2'percent lead, said composition havinga metallographic. structure small particles-when said explosive material'is fired.

References Citedin the file ofthis patent UNITED STATES PATENTS,

I Lawson Aug. 5, 19.52

; 2,667,836 Church et' a1. Feb. 2, 1954 FOREIGN PATENTS 551,007 Belgium Sept. 29, 1956 677,824 Great Britain Aug. 20,1952

OTHER REFERENCES.

, American 'Institute of Mining and Metallurgical Engineers, Technical Publication No. 2158, Class A, Mining Technology, 1947, Behavior of Metal Cavity .Liners in Shaped Explosive Charges.

consisting of copper dendrites with the spaces be-; 

1. A LINED, SHAPED EXPLOSIVE CHARGE COMPRISING: (A) A BODY OF EXPLOSIVE MATERIAL PROVIDING A CAVITY IN A FACE THEREOF; AND (B) A METAL LINER COVERING THE FACE OF SAID CAVITY, SAID METAL LINER COMPRISING A COMPOSITION CONSISTING ESSENTIALLY OF FROM 75 PERCENT TO 99.5 PERCENT COPPER AND FROM 25 PERCENT TO 0.5 PERCENT LEAD, SAID COMPOSITION HAVING A METALLOGRAPHIC STRUCTURE CONSISTING OF COPPER DENDRITES WITH THE SPACES BETWEEN SAID DENDRITES FILLED WITH LEAD, SAID LINEAR BEING ADAPTED TO BREAK UP SUBSTANTIALLY COMPLETELY INTO SMALL PARTICLES WHEN SAID EXPLOSIVE MATERIAL IS FIRED. 